<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    header {
      background-color: pink;
    }

    .main {
      width: 100%;
      float: left;
      background-color: skyblue;
    }

    .center {
      margin: 0 100px;
    }

    .left {
      width: 100px;
      background-color: green;
      float: left;
      margin-left: -100%;
    }

    .right {
      width: 100px;
      background-color: red;
      float: left;
      margin-left: -100px;
    }

    footer {
      background-color: pink;
      clear: both
    }
  </style>
</head>

<body>
  <header>头部</header>
  <div class="main ">
    <div class="center">主区域</div>
  </div>
  <div class="left ">左区域</div>
  <div class="right ">右区域</div>
  <footer>底部</footer>

</body>

</html>